It is known that certain metal alloys are heatrecoverable, that is to say, when a suitably heat-treated article of one shape made from such an alloy is caused to deform into another shape at an appropriate temperature and the article is subsequently heated to a sufficiently higher temperature, the article will at least partly recover its original shape. This change of shape on reheating corresponds to a change of phase in the alloy from a low-temperature phase to a high-temperature phase. The phenomenon of heat recoverability is known to occur with articles made from nickel-titanium binary containing 52 - 56 percent by weight of nickel and also with certain gold-cadmium and cadmium-silver-gold alloys.